1. Field of the Invention
The present invention relates to a method for converting a video signal such as a television signal into a digital high-efficiency coded signal and transmitting it, a video signal transmission apparatus for use in the method, and a video signal reception apparatus.
2. Description of the Related Art
In recent years, a system for transmitting and receiving a high-resolution television signal (hereinafter referred to as a high-resolution TV signal) has been developed as a new method for transmitting and receiving a TV signal. The high-resolution TV signal has a larger number of scanning lines than that of scanning lines of a TV signal of the currently-used NTSC system (hereinafter referred to as a low-resolution TV signal), and allows an image to be formed more clearly.
To watch high-resolution television, a high-resolution television set for receiving and demodulating a high-resolution TV signal is needed. Since, however, most of viewers have NTSC television sets, if they replace the NTSC television sets with high-resolution television sets, the NTSC television sets will be useless, as will be program sources of the NTSC system. Therefore, producers of TV programs wish to transmit the low-resolution TV signals as well as the high-resolution TV signals. If, however, a transmission path for the high-resolution TV signal and a transmission path for the low-resolution TV signal are formed separately from each other, it is difficult to assign transmission bands to these transmission paths.
In order to popularize the methods for transmitting and receiving a high-resolution TV signal, television sets, such as HDTV (high definition television) sets and NTSC television sets, that the viewers possess at present, need to be used effectively. Further, it is necessary to devise the methods so as not to make program video sources of the NTSC system useless.